The Poisson's Problems on graphs

In this paper we study the problem $$\begin{cases} -\Delta_d u = \mu_0 &\text{ in } G\\ u = 0 &\text{ on } \partial G \end{cases}$$ where, $\Delta_d$ represent the discret Laplacian, and $\mu_0$ it is a measure defined in the vertex of the graph $G=(V,E)$. Here $V$ defined the vertex of the graph, $E$ its edges and $\partial G$ its boundary. We prove that this problem has an unique solution by using an adaption of the Perron's method for the graphs by using an idea known as Balayage.